The healthcare sector's drop in the past year means investors can buy many healthcare stocks on sale, including these five stocks. All five could experience explosive growth in 2017, and they are trading at share prices below 2016's peak. 

Read on to find out if now is the right time to add Exact Sciences (EXAS 1.93%), Kite Pharma (NASDAQ: KITE), Illumina (ILMN 0.30%), GW Pharmaceuticals (GWPH), and Sarepta Therapeutics (SRPT 30.14%)to your portfolio.

Image source: Getty Images.

No. 1: Game-changing new screening test

Exact Sciences is changing how millions of older Americans get screened for colon cancer, and that's creating a multibillion-dollar opportunity for investors. The company markets a screening test that is cheaper and far less invasive than a colonoscopy, and that test -- Cologuard -- is quickly winning over doctors, patients, and insurers. It completed 244,000 Cologuard tests last year, and that figure is climbing as insurers embrace reimbursement following the test's inclusion on national colon cancer screening guidelines last year.

With the number of completed tests increasing 134% year over year in 2016, and that momentum is building as more doctors prescribe it. This year could be a breakout year for Exact Sciences in terms of both sales and profit. Last year, the company pocketed $99 million in sales, but management believes this market could be worth $4 billion. If test volume continues to accelerate and management can keep a lid on expenses, this company could exit 2017 at a sales run rate that positions it for profitability in 2018.

No. 2: Exciting new development in fighting cancer

Heralded as the next big thing in cancer treatment, CAR-T therapies that reengineer a patient's immune system to better find and destroy cancer cells could be become a reality in 2017.

Kite Pharma has already started completing its rolling Food and Drug Administration application for approval of KTE-C19, a CAR-T therapy for non-Hodgkin lymphoma, and that suggests this game-changing medicine could become available for widespread use before year's end.

If approved, KTE-C19, which will be marketed under the brand name Axi-Cel, will offer new hope to thousands of patients with B-cell cancers that have returned or failed to respond to existing therapies. In the U.S., Axi-Cel's addressable patient population is 7,400, and there are another 7,000 addressable patients in the E.U., where Kite Pharma plans to file for Axi-Cel's approval this year. 

Since Axi-Cel could have first-mover advantage and it's a complex approach, it's likely to command top-tier pricing, and that suggests to me that it could be a nine-figure selling drug out of the gate. If I'm right, then owning shares in this innovative biotech could be profit-friendly this year.

No. 3: Disruptive new technology launching soon

One of the biggest potential advances expected in medicine in the coming decade is personalized medicine that's tailored specifically to each person's genetic makeup. When it comes to developing new gene therapies and screening patients for an amenable genetic make up, Illumina is likely to be a big beneficiary.

Illumina's machines are the gold standard in gene sequencing, and its innovation over the years has led to lower gene-sequencing costs and a corresponding surge in gene research. For instance, when Illumina launched its HiSeq X a few years ago, it revolutionized the market by reducing the cost of sequencing a genome to $1,000. 

Image source: Illumina.

This year, Illumina's at it again. It's launching the NovaSeq 6000, a system that could help push the cost of sequencing to as little as $100.

Because the price of sequencing could be about to fall dramatically and these machines can sequence genes more quickly and more thoroughly than ever before, researchers could be on the cusp of making new discoveries that could profoundly impact patient treatment. 

Given the potential for lower sequencing costs to spark another surge in sequencing demand, Illumina's one of my favorite growth stocks to buy in 2017.

Image source: Getty Images.

No. 4: Marijuana as medicine approaches the finish line

Pro-pot advocates have touted marijuana's ability to help epileptics for years, but in 2016, GW Pharma became the first drugmaker to prove in scientifically controlled studies that marijuana effectively treats these patients.

The company reported data from three separate trials last year, and each showed that GW Pharma's purified CBD, a chemical cannabinoid found in marijuana, reduces monthly seizures in Dravet and Lennox-Gastaut syndrome patients, by about 40%.

GW Pharma expects to file for FDA approval of Epidiolex in the first half of 2017, and if the FDA gives the company a green light, then Epidiolex could become commercially available in late 2017 or early in 2018. While the addressable market in Dravet and Lennox-Gastaut syndrome is small, GW Pharma estimates that one-third of the 477,000 children with epilepsy respond inadequately to existing treatments. 

With a potential launch coming, and a big opportunity to treat more of patients over time, this year could be just the beginning for GW Pharma.

No.5: Overcoming objections

Patients with Duchenne muscular dystrophy (DMD) face limited treatment options, and because of the damage caused by this disease to their cardiovascular system, a shortened lifespan. However, the FDA approval of Exondys 51 last summer may offer new hope to hundreds of patients in 2017.

Exondys 51 is the first treatment that's designed the genetic mutations that cause this muscle-wasting disease, and while it isn't designed for use in every DMD patient, it may help delay disease progression in about 13% of them.

In July, Exondys 51 secured approval after a contentious debate over its efficacy, and at $300,000 per year, it won't take many patients to begin using this drug to shore up Sarepta Therapeutics' financials. 

So far, negotiations with insurers, and screening patients to confirm that they have an amenable genetic makeup, has resulted in limited sales. However, management recently offered up insight at a key healthcare conference that suggests its making progress on both fronts. In addition to reporting progress with insurers that includes pending decisions by insurers covering 79% of patients, 250 children have begun start forms to be able to begin receiving Exondys 51 once decisions are issued.

If insurers get on board and the number of patients receiving Exondys 51 climbs, it could provide an important source of tens of millions of dollars in revenue to support research that could expand Sarepta Therapeutics' approach to more DMD patients. Admittedly, it's unlikely this company will turn a profit anytime soon, but it could make progress toward that goal this year, and that makes it a stock worth considering.